Selective separation of selenium (IV) by thiol cellulose powder and subsequent selenium isotope ratio determination using multicollector inductively coupled plasma mass spectrometry

An efficient matrix separation procedure for the removal of hydride-forming elements such as As, Ge and Sb and transition metal ion interferences is described for the determination of selenium isotope ratio by hydride generation coupled to multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). The preconcentration of Se ions by thiol cellulose powder (TCP) was studied by both batch and column methods. The selective separation of Se (IV) from the interferences was achieved with a column method using 0.10 g of TCP and eluting the interfering species with dilute hydrochloric acid prior to analysis. A recovery of ≥ 98 % was obtained using the column method. The procedure was also used to evaluate the degree of pre-concentration of Se on the TCP. The degree of pre-concentration was linearly proportional to the amount of sample passed through the column. Se retained on the TCP was quantitatively recovered by digesting twice with small volumes (50 μL) of concentrated nitric acid. The complete elimination of interfering elements and the marked gain in sensitivity allowed high precision Se isotope ratios measurements in lake-sediments and certified reference materials using hydride generation (HG) coupled to MC-ICP-MS. The estimated external precision achieved for δ78Se (‰) by HG-MC-ICP-MS after sample pre-concentration and matrix removal with TCP columns varied between 0.15‰ and 0.21‰ using a double spike correction approach.